“…Its Poincaré axis, n d , appears, its degree of polarization, p d , does not; but, in this respect, we have at hand the basic Equation (9). Evidently, when dealing with dichroic devices, we use full hyperbolic trigonometry and geometry, and, in processing further Equation (17), we have to use the relationships between the hyperbolic functions. We could continue on this inductive way, changing the unexpressive (in this context) hyperbolic parameter η with the degree of dichroism, p d , all the more since cosh η also leads to something expressive:…”